Using a chef's knife, trim the unpeeled potatoes into rectangular blocks.,Cut each into 1/4-inch thick slices.,Stack two or more slices together and cut into 1/4-inch julienne strips.,Cut these strips into 1/4-inch dice and place in a saucepan, covered with cold water, until ready to cook.,Place the potatoes in cold water, bring to a boil, then immediately take off the heat and drain.,Allow the potatoes to air dry.,Meanwhile, prepare the persillade by mixing together the garlic and parsley.,______,If the potatoes aren't thoroughly dry, blot them with towels.,Heat the oil in a very large skillet over medium heat.,Add the potatoes and cook, tossing occasionally, until they brown lightly, 6 to 8 minutes.,You may drain and discard oil at this point, if desired.,Add the butter and continue sauteing for another 5 minutes or longer to brown the potatoes completely.,Just before serving, toss the potatoes with the garlic and parsley over medium heat for about 1 minute.,Season with salt and pepper.,Serve immediately.